Centos 开启telnet-service服务
1. 查看linux版本信息:
[loong@localhost ~]$ cat /etc/issue
CentOS release 5.8 (Final)
Kernel \r on an \m
2. 查看系统是否已安装telnet-server,linux系统上默认已经安装telnet-client(或telnet),而telnet-server需要手动安装。
[loong@localhost ~]$ rpm -qa | grep telnet
telent-server-xx
telnet-0.17-39.el5
3.如果上边显示已经有telent-server-xx若系统已安装,跳过此步。安装telnet-server。
方法一:下载RPM resource telnet-server,下载地址:http://rpmfind.net/linux/rpm2html/search.php?query=telnet-server
选择相应版本的telnet-server下载;
安装:# rpm -i telnet-server-0.17-39.el5.i386.rpm #貌似还得单独安装xinetd.
方法二:(推荐使用)
# yum install telnet-server
安装完成后:
[loong@localhost ~]$ rpm -qa | grep telnet
telnet-0.17-39.el5
telnet-server-0.17-39.el5
4. 启动telnet服务 (推荐方法三)
方法一:System->Administration->Services 中,
在On Demand Services中选中telnet,
并在Background Services中选中xinetd,并点击上面的Start,即在右侧显示:xinetd (pid 15986) is running...
最后Save & Quit.
方法二:编辑/etc/xinetd.d/telnet, 将其中的 disable = yes 的yes改为no.
修改后:
# default: on
# description: The telnet server serves telnet sessions; it uses \
# unencrypted username/password pairs for authentication.
service telnet
{
disable = no
flags = REUSE
socket_type = stream
wait = no
user = root
server = /usr/sbin/in.telnetd
log_on_failure += USERID
}
方法三:使用chkconfig命令直接开启
[root@localhost loong]# chkconfig telnet on
注:方法二和方法三,需要激活xinetd服务。方法如下:
[root@localhost loong]# service xinetd restart
Stopping xinetd: [ OK ]
Starting xinetd: [ OK ]
或:
[root@localhost loong]# /etc/rc.d/init.d/xinetd restart
Stopping xinetd: [ OK ]
Starting xinetd: [ OK ]
5. 测试服务
[root@localhost loong]# telnet localhost
Trying 127.0.0.1...
Connected to localhost.localdomain (127.0.0.1).
Escape character is '^]'.
CentOS release 5.8 (Final)
Kernel 2.6.18-308.1.1.el5 on an i686
login: loong
Password:
Last login: Tue Apr 24 16:42:06 from 10.108.14.135
[loong@localhost ~]$ exit
logout
Connection closed by foreign host.
[root@localhost loong]#
到此 telnet Ctrl+]打开回显功能,enter即可
注:默认情况下,系统只允许普通用户telnet登录,不允许root用户登录。
要想获得root权限,可以使用普通用户登录,然后执行su,来获得root权限。
或使用一下方法,允许root登录telnet:
方法一:# mv /etc/securetty /etc/securetty.bak (不建议这种方法,测试完后再改回去吧!)
或先试图使用root用户登录,不成功,然后查看系统log:
telnet> o localhost
Trying 127.0.0.1...
Connected to localhost.localdomain (127.0.0.1).
Escape character is '^]'.
CentOS release 5.8 (Final)
Kernel 2.6.18-308.1.1.el5 on an i686
login: root
Password:
Login incorrect
login:
Login incorrect
login:
Login incorrect
login:
Connection closed by foreign host.
[root@localhost loong]# tail -20 /var/log/secure
Apr 24 17:32:58 localhost login: pam_securetty(remote:auth): access denied: tty 'pts/1' is not secure !
Apr 24 17:33:03 localhost login: FAILED LOGIN 1 FROM localhost FOR root, Authentication failure
可以看到 access denied: tty 'pts/1' is not secure !
所以将‘pts/1’添加到/etc/securetty中,即可实现telnet的root用户登录。至于为什么?暂不清楚。
方法二:修改/etc/pam.d/remote,注释掉:auth required pam_securetty.so
1 #%PAM-1.0
2 #auth required pam_securetty.so
3 auth include system-auth
注:不建议开放telnet的root登录,容易带来安全隐患。
参考连接:
1. http://wenku.baidu.com/view/105544aedd3383c4bb4cd23d.html
2. http://www.5dlinux.com/article/9/2008/linux_16136.html
3. win7下使用telnet命令:http://wenku.baidu.com/view/f0ff731152d380eb62946d9d.html